Silicone rubber tubing, because of its relatively high temperature performance, water and weather resistance and other characteristics, is highly desirable in a number of applications.
Detracting from the usefulness of silicone rubber tubing is its lack of strength and its lack of resilience after extended compressive loading, referred to sometimes as compression set.
Because of the aforesaid beneficial properties, silicone rubber is especially desirable for use in combination with metal wire as gasketing to provide shielding against electromagnetic impulse ("EMI") and radio frequency interference ("RFI") forms of electromagnetic interference. Because of the lack of adhesion generally between silicone and metal, one method which has been employed for combining these materials to provide EMI/RFI shielding gasketing has been to merely assemble separate silicone and metal wire elements in a coaxial relation. A second method employed to combine these materials has been to embed a multiplicity of spaced, parallel wires in a solid sheet of silicone.
A major drawback of both types of constructions is that they cannot be conveniently provided in continuous, seamless tubing.
Other drawbacks of the former type of construction, particularly when used as gasketing, are that the metal and silicone may separate and the metal, generally being exposed on the outer surface of the silicone, may fray and break if the device is used, for example, to gasket an element such as a door, lid, or panel which is repeatedly opened and closed against the device.
Another apparent drawback of the latter type of construction is that the density at which the wires is provided, typically more than 600 wires per square inch, must require the fabrication and use of incredibly complicated, delicate and expensive fixtures or molds.
The foregoing disadvantages are overcome by the present invention which provides certain additional benefits including, but not limited to, composite flexible plastic tubing with greater strength, greater resilience and greater resistance to compression set than the plastic material would provide alone, particularly silicone tubing, and further a new form of metal impregnated plastic tubing, particularly silicone plastic tubing, for EMI/RFI shielding, particularly when used as gasketing to provide such shielding.